The present disclosure relates generally to image sensors and, more particularly, to complementary metal-oxide-semiconductor (CMOS) image sensors.
In semiconductor technologies, image sensors are used for sensing a volume of exposed light projected towards a semiconductor substrate. Complementary metal-oxide-semiconductor (CMOS) image sensors (CIS) and charge-coupled device (CCD) sensors are widely used in various applications such as digital still camera applications. These devices utilize an array of pixels or image sensor elements, including photodiodes and transistors, to collect photo energy to convert images into electrical signals.
However, image sensor devices suffer from dark current. That is, unwanted current generated by pixels in the absence of illumination. There may be different sources of dark current such as impurities in the silicon wafer, damage to the silicon crystal lattice by processing techniques, and heat build up in the pixel area. Excessive dark current may lead to image degradation and poor device performance.
Therefore, what is needed is a simple and cost-effective method and device for reducing dark current in image sensors.